1. Field of the Invention
The present invention relates to a lithography process in manufacturing a semiconductor device, more particularly to a pattern forming method in a multilayered resist process, an underlayer film forming composition, and a method of manufacturing a semiconductor device.
2. Description of the Related Art
In recent years, accompanying miniaturization of a semiconductor device, a multilayered resist pattern forming method has been performed in order to cope with a reduced resist film thickness and a lacking mask resistance. In the multilayered resist pattern forming method, a film constituted of three layers of an underlayer film/an intermediate film/a resist film is formed on a film to be worked formed on a wafer substrate, and a resist pattern is successively transferred to an intermediate layer/the underlayer film/the film to be worked.
In this method, first the underlayer film is formed which is an anti-reflection film to absorb an underlayer stepped portion sufficiently, an intermediate layer such as spin on glass (SOG) having the mask resistance is formed on the underlayer film, and the resist film is further formed on the intermediate layer.
Next, the resist film is patterned by photolithography, and the pattern is transferred onto the intermediate film by etching using the patterned resist film as a mask. Furthermore, the pattern is transferred onto the underlayer film by the etching using the patterned intermediate film as the mask, and finally the film to be worked is worked by use of this underlayer film as the mask.
In this method, since cracks are generated in the underlayer film after applying a solution during formation of the underlayer film, in general, a crosslinking agent is added to an underlayer film forming composition. Examples of the crosslinking agent include multinuclear phenol, and various commercially available hardeners such as an epoxy compound, a melamine-based hardener, and a glycoluril-based hardener. However, when the crosslinking agent is excessively added, contents of elements such as O, N, and H having high reactivity to the etching increase in polymer, and there is a problem that an etching resistance of the underlayer film deteriorates.
Moreover, in Jpn. Pat. Appln. KOKAI Publication No. 2002-198295, there is disclosed a pattern forming method in which a carbon-containing underlayer film is formed by a multilayered resist process, and the underlayer film is coated with an intermediate film containing a silicon compound including Si—Si bonding as a main chain and having a desorbing property.